Heater issue

[BigShowJoe]

2000 New Tahoe LS. Front heat is cold but rear heat is hot. After 30-45 min of driving, the front heat gets a little warm but never hot. Both lines connecting to the heater core are too hot to hold on to. Inlet seems a little hotter but the outlet is still very hot. I am assuming the blend door is working because even though the front is cold, there is still a noticeable, colder, difference when turning the knob from red to blue. Any help is appreciated.

 

[Chevy305]

Do you feel an air flow different when you go from cold to hot? You could have something blocking the heater core. I'd start with the easy thing and check your cabin filter.

 

[BigShowJoe]

Do you feel an air flow different when you go from cold to hot? You could have something blocking the heater core. I'd start with the easy thing and check your cabin filter.

Air flow is the same regardless of where the temp knob is set.

 

[clandr1]

Sounds like your blend actuator has gone bad. Search the forum for two things:
1. Actuator reset sequence, and if that doesn't work...
2. Front actuator replacement

 

[BigShowJoe]

Sounds like your blend actuator has gone bad. Search the forum for two things:
1. Actuator reset sequence, and if that doesn't work...
2. Front actuator replacement

You believe a bad blend actuator even though I DO notice some difference in air temperature between cold and hot?

 

[Trixxterr]

WELL, isnt that the kicker, I just came here looking for clues to this same issue. One catch. Blend door is CONFIRMED working. mine was about a 1/4 gallon low coolant, thermometer in vent shows 80*. but doesnt feel like it. Rear Is blazing HOT, Front Luke warm. Starting to think maybe and air bubble in core? or maybe core blockage?

Oh, All this started. About a week ago, Prior to that worked perfectly.. One day it worked fine, The next not so much..

 

[BigShowJoe]

WELL, isnt that the kicker, I just came here looking for clues to this same issue. One catch. Blend door is CONFIRMED working. mine was about a 1/4 gallon low coolant, thermometer in vent shows 80*. but doesnt feel like it. Rear Is blazing HOT, Front Luke warm. Starting to think maybe and air bubble in core? or maybe core blockage?

Oh, All this started. About a week ago, Prior to that worked perfectly.. One day it worked fine, The next not so much..

Mine has been like this for a while now. I'm going to reverse flush the core this weekend. Hoping that fixes it.

 

[clandr1]

You believe a bad blend actuator even though I DO notice some difference in air temperature between cold and hot?

Yes. It's very possible the door is opening only slightly, allowing some warm air in, but not fully opening.

Since you said the inlet and outlet lines are both extremely hot, I think you're wasting your time with a heater core flush. The flow is probably fine.

 

[BigShowJoe]

Yes. It's very possible the door is opening only slightly, allowing some warm air in, but not fully opening.

Since you said the inlet and outlet lines are both extremely hot, I think you're wasting your time with a heater core flush. The flow is probably fine.

Is there a write-up somewhere on how to check it?

 

[clandr1]

Is there a write-up somewhere on how to check it?

The first part details replacement, but there is a paragraph at the bottom of the first post that shows the reset method. Try that first.

http://www.tahoeyukonforum.com/forum/showthread.php?t=15787